Asp.net DropDownList Server Control

DropDownList Control

A DropDownList is also commonly known as combo box. It can contain multiple data members, but unlike a normal list box the users can choose only one value from this control. Though the functionality of this DropDownList is much like a Single Row Select List Box, a DropDownList can save a lot of GUI space as it is rendered on a Single line and is expanded only when the user clicks on the Control.
   This DropDownList is provided as a Server Control in ASP .Net like many other controls. This DropDownList can be used to add data manually or even for dynamic binding with data base.

Example first

Example 1^st:

Adding data in DropDownList using property(Items collection)

<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True">

        <asp:ListItem>---Select city---asp:ListItem>

        <asp:ListItem>Madhubaniasp:ListItem>

        <asp:ListItem>Darbhangaasp:ListItem>

        <asp:ListItem>New Delhiasp:ListItem>

    asp:DropDownList>

Example 2^nd :

Adding data in DropDownList using DataBind(database)

Source code

<asp:DropDownList ID="DropDownList2" runat="server">

        asp:DropDownList>

Code File

protected void Page_Load(object sender, EventArgs e)

    {

        SqlConnection con = new SqlConnection("Trusted_connection=true;database=pubs");

        SqlDataAdapter da = new SqlDataAdapter("Select * from authors",con);

        DataSet ds = new DataSet();

        da.Fill(ds);

        DropDownList2.DataSource = ds;

        DropDownList2.DataTextField = "city";

        DropDownList2.DataBind();

    }

Example 3^rd :

Source code]

<asp:DropDownList ID="DropDownList3" runat="server" AutoPostBack="True">

            <asp:ListItem>---Select city---asp:ListItem>

            <asp:ListItem>Madhubaniasp:ListItem>

            <asp:ListItem>Darbhangaasp:ListItem>

            <asp:ListItem>New Delhiasp:ListItem>

        asp:DropDownList>

        <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Ok"

            Width="96px" />

        <asp:Label ID="Label1" runat="server">asp:Label>

Code File

protected void Button1_Click(object sender, EventArgs e)

    {

       Label1 .Text ="You have selected "+ DropDownList3.SelectedItem.Text;

    }

Example 4^th :

Source code

<asp:DropDownList ID="DropDownList4" runat="server" AutoPostBack="True"

            onselectedindexchanged="DropDownList4_SelectedIndexChanged">

            <asp:ListItem>---Select city---asp:ListItem>

            <asp:ListItem>Madhubaniasp:ListItem>

            <asp:ListItem>Darbhangaasp:ListItem>

            <asp:ListItem>New Delhiasp:ListItem>

        asp:DropDownList>

        <asp:Label ID="Label2" runat="server">asp:Label>

Code File

protected void DropDownList4_SelectedIndexChanged(object sender, EventArgs e)

    {

        Label2.Text = "You have selected " + DropDownList4.SelectedItem.Text;

    }